1. Field of the Invention
The present invention relates to an image forming apparatus having a function of supplying lubricant on an image carrier, and an image forming method in an image forming apparatus.
2. Description of the Related Art
Electrophotographic image forming apparatuses, such as multifunctional peripherals, copying machines, or printers, have been widely used conventionally. Such an electrophotographic image forming apparatus generally includes an image carrier having a surface on which a toner image is formed while being rotationally driven, a transfer device transferring the formed toner image to a transfer body or a medium, and a cleaning member recovering remaining toner on the surface of the image carrier after the toner image is transferred, and cleaning the surface of the image carrier.
As the image carrier, a photoreceptor is used. A cycle is repeatedly performed on the photoreceptor. The cycle includes a charging step of uniformly charging the surface of the photoreceptor, an exposure step of exposing the surface of the photoreceptor according to a specified image pattern and forming an electrostatic latent image, and a development step of supplying toner to the image carrier and developing the electrostatic latent image.
Further, in order to reduce a friction force generated between the cleaning member and the image carrier, a lubricant supply mechanism is generally provided which supplies lubricant on the image carrier. As the lubricant, a metal soap such as a metal stearate is generally used. The lubricant supply mechanism is known which is provided with an application mechanism including a brush on the upstream or downstream side of the cleaning member, supplies lubricant at a developing unit, adding the lubricant to toner, or has a combination thereof. The lubricant supply mechanism is provided to apply lubricant to the surface of the image carrier, and thus, a frictional coefficient is reduced with respect to toner on the surface of the image carrier. Reduction of the frictional coefficient inhibits transfer failure upon transfer of the toner image formed on the surface of the image carrier to a transfer material or the like, and the quality of the toner image can be increased. Further, a frictional coefficient between the image carrier and a member (e.g., cleaning blade or the like) making pressure-contact with the image carrier is also reduced, and thus, abrasion (scraping) on the surface of the image carrier is effectively inhibited, and the life of the image carrier can be also extended
For example, in JP 2002-006689 A, an image forming apparatus is disclosed. The image forming apparatus supplies lubricant to an image carrier forming a toner image to extend the life thereof and increase image quality. More specifically, an image forming apparatus disclosed in JP 2002-006689 A temporarily recovers lubricant on a photoreceptor, raises a frictional coefficient, and then supplies lubricant, in order to remove a discharge product on a photoreceptor.
Further, in JP 2014-142472 A, an image forming apparatus is disclosed which can reduce a difference in level of a photoreceptor caused by abrasion. More specifically, the image forming apparatus disclosed in JP 2014-142472 A obtains an amount of images integrated by integration of gradation values of image information corresponding to a plurality of blocks. The blocks are obtained by dividing an image formed on a photoreceptor in a rotational axis direction (longitudinal direction) of the photoreceptor. Then, the image forming apparatus specifies a position of the photoreceptor in the rotational axis direction, and predicts the generation of a difference in level on the photoreceptor caused by abrasion. Next, the image forming apparatus forms a ZnSt supply image at the predicted position to supply ZnSt particles, and prevents the surface of the photoreceptor from being further abraded at this position.
Although lubricant is not supplied, in JP 2007-240768 A, an image forming apparatus is disclosed which supplies an appropriate amount of toner only to a position having a reduced amount of toner on the image carrier, and shows the maximum performance of the cleaning blade.
In contrast, a lubricant layer including lubricant deteriorates due to a discharge product generated in the charging step or the like, and the lubricant layer itself also deteriorates due to change in quality of the lubricant itself. Such deterioration may reduce the resistance of the lubricant layer and generate a blurred image, or lose the lubricity of lubricant (effect of reducing a friction force) and generate abnormal abrasion of the cleaning blade.
For example, in JP 2006-259031 A, an image forming apparatus is disclosed which is provided with a lubricant removing mode on an image bearing member, deteriorated due to discharge from a charging device, and can prevent deterioration in quality of images or generation of an abnormal image. More specifically, the image forming apparatus disclosed in JP 2006-259031 A is provided with a lubricant removing device and a lubricant supplying device on a photoreceptor, and uses toner as the removing device.
In terms of not lubricant but the removal of foreign matter such as paper dust, a configuration is disclosed in JP 2013-101169 A. The configuration removes the foreign matter such as paper dust accumulated in an abutment portion between a cleaning blade and an intermediate transfer belt without reducing productivity, and secures slidability of the cleaning blade to the intermediate transfer belt.
However, in the above-mentioned related art, the deteriorated lubricant cannot be fully removed, and the blurred image or the abnormal abrasion of the cleaning blade may occur. This phenomenon is considered to be caused by deterioration of the lubricant layer not separated by toner supplied during normal image formation and rigidly stuck on the image carrier.